Interference fit case construction



Dec-9,1969 F) c: HITZEROTH ET AL 3,482,727

INTERFERENCE FIT CASE CONSTRUCTION Filed'April 16, 1968 INVENTORS FRANKLIN c HITZEROTH D VID WA T'ZER ATTORNEY United States Patent 3,482,727 INTERFERENCE FIT CASE CONSTRUCTION Franklin C. Hitzeroth and David B. Walitzer, Centerville, Iowa, assignors to McGraw-Edison Company, Elgin, 11]., a corporation of Delaware Filed Apr. 16, 1968, Ser. No. 721,695 Int. Cl. B65d 7/00 US. Cl. 220-4 3 Claims ABSTRACT OF THE DISCLOSURE A case construction having two or more elements secured together at spaced areas of engagement, with one area of engagement including a tab formed on one element and having a camming surface that, upon assembly of the elements, rides over an interfering edge on the other element and which thereby loads the two elements as between are areas of engagement under respective tension and compression forces, and a locking shoulder on the tab that engages the other element to prevent the removal of the tab past the interfering edge.

Many elecrical appliances such as toasters, warmers, broilers, etc. have a case formed by two or more separate elements that are secured together. It has been common place to interlock the separate elements by means of fitting a tab on one element through a cooperating opening in the other element, and thereafter of mechanically deforming the end of the tab by folding or twisting it against the other element. The deformed tab precludes the withdrawal of the tab from the opening, and thus holds the elements together to define the case.

This general means of holding together the separate elements of the case is deficient in several ways. In the first place, the necessity of deforming the tab limits the configuration of the elements, since after assembly a tool of some sort must be inserted behind the receiving opening to deform the tab. Secondly, the step of deforming the tab added to the normal case assembly increases the cost in the amount of additional equipment and time required for such step. Thirdly, the case construction sometimes is not really solid and tight fitting since minor excess clearances between the tab and opening allow the elements to shift relative to one another by this clearance.

This invention relates to an improved case construction having two or more elements that are assembled and held together to form the case, and more particularly, to an improved means for holding the elements together without any required deformations of the elements.

An object of this invention is to provide an improved case formed from two elements whereby one element has a tab with a camming surface that can be biased, during assembly of the two elements, against an interfering edge on the other element to load the elements under respective tension and compression forces, and further to means such as a locking shoulder on the tab which precludes the removal of the tab to maintain the elements under the tension and compression forces and locked together.

This and other objects will be more fully understood and appreciated after reviewing the following specification including the accompanying drawing, wherein:

FIG. 1 is a perspective view of a typical toaster case having one embodiment of the subject invention incorporated therein;

FIG. 2 is a perspective view, similar to FIG. 1, showing the separate elements of the toaster case in preassembled relationship;

FIG. 3 is an enlarged sectional view, as seen generally from line 33 in FIG. 1;

3,482,727 Patented Dec. 9, 1969 FIG. 4 is a sectional view, as seen generally from line 4-4 in FIG. 3; and

FIGS. 5 and 6 are views corresponding generally to FIGS. 3 and 4, respectively, showing an alternate embodiment of the subject invention.

Referring now to FIG. 1, a typical toaster 10 is shown upon which the subject invention can be incorporated. The toaster 10 includes a metal case or body 12 having plastic or other insulating combination handle-pedestal elements 14 secured thereto by appropriate means (not shown). The case 12 is hollow, as is well known, and top openings 16 communicate with and are aligned with bread receiving slots (not shown) formed in the toasting mechanism 20 (FIG. 3) of the toaster. The toasting mechanism 20 is disclosed only diagramatically since it can be any known construction and forms no part of this invention. The toasting mechanism has flanges 22 formed thereon which overlap and are secured against flanges 24 formed from the bottom of the case. Bread lowering handle 26 (FIG. 1) and temperature control knob 28 are typically incorporated as part of the toaster extending through openings in the case, and being connected to the toasting mechanism 20.

This invention relates to an improved construction for the case 12. Briefly, U-shaped element 30 having three panels 32 and 34 which are connected together along corner folds 33, and the two elements 38 (only one being shown) fitted between opposing edges of and secured to element 30 define the five sided-open bottom case construction.

Referring now to the assembled cooperation of elements 30 and 38, note that each top opening 16 is formed in part by turning in from edge 39 portion 40 (FIG. 3) of the top panel 34. A top marginal flange 42 is folded at corner 43 from the top panel 34 and further has an inwardly disposed leg terminating at edge 44. Each side panel 32 similarly has a marginal flange 46 folded in from the respective corner edge 47, and a leg inwardly directed from the flange terminates at edge 49, except at its lower end which there extends further to define a tap 50, best seen in FIGS. 2, 3 and 4.

Each element 38 is basically similar, except for possible trim, and includes top flange 54 and side flanges 55, the top flange engaging at its free edge 56 portion 40 from element 30. After a narrow top marginal band 58 and narrow side marginal bands 60 the element 38 flairs outwardly and thereafter continues uniformly throughout most of the remainder portion of the panel. The free flange edges 44 and 49 of the element 30 engage the marginal bands of element 38 adjacent the flaired central portion and give thereby the appearance of a single piece case. Element 38 is directed inwardly at its lower end to define the flange 24 to which the toasting mechanism 20 is secured, as noted above. Each element 38 has two openings 64 which receive the tabs 50 formed on element 30 and thereby are in general alignment with its respective tab when the elements are positioned to be assembled together.

When top portions 54 of element 38 is against the top panel 34 of element 30 and between inturned wall 40 of element 30 and the flange edges 44 and 49, at least the tops of the elements 30 and 38 are confined laterally of one another; and further element 38 cannot be moved upwardly relative to element 30. This defines a first area of engagement.

Referring now specifically to FIG. 3, the tab 50 will be seen to include a leading camming surface 66 which slopes at an angle relative to the element 38, a locking shoulder or surf-ace 68 which angles in the opposite direction from the camming surface 66, and a generally flat surface 70 which extend to the interior edge 49. The 0pening 64 has an interfering edge 72 which is spaced relative to the carnming surface 66 and the first area of engagement to engage the ca-mming surface midway along its length, so that the end of the tab can be freely inserted Within the opening upon initial assembly of the elements.

During assembly of the elements 30 and 38 to form the case 12, the upper areas of the elements are fitted in place as the first area of engagement, and the free end of each tab 50 is thereafter inserted into its receiving opening 54 formed on the element 38. The camming surface 66, upon engaging and being moved past the interfering edge 72, exerts as between the first area of engagement and the tab or second area of engagement a tension force in the panels 32 of element 30 and a compression force in each element 38. The flat engaging surfaces 70 maintain the elements under mutual compressive and tension forces when engaged with the interfering edge. The locking shoulder 68 engaging the side of the element 38 remote from panel 32 prevents removal of the tab from the opening. The respective compression and tension forces between the elements hold the elements securely and prevents shifting, and the tabs need not be deformed in any manner.

FIGS. and 6 show an alternate case embodiment formed with elements 78 and 80. In this embodiment, element 80 is U-shaped and has side panels 82 and top panel 84 connected together. Top flange 86 extends from the top panel 84, and side flanges 88 extend from respective side panels 82. Opposed bottom flanges 90 extend from the respective side panels 82 and are used for corn neetion of toasting mechanism (not shown). Openings 92 are spaced apart along the top flange 86, and an opening 94 is formed in each side flange 88.

Each separate element 78 is generally planar and has its marginal edges rolled over as at top roll 98 and adjacent side rolls r100. Locking tabs 102 project from the top roll 98 at spacings corresponding to flange openings 92, and are adapted to be fitted through these openings and engage and interlock with the top flange. Tabs 104 are similarly defined as projections from the side rolls 100 and are adapted to be received within the openings 94.

Upon assembly of the case, tabs 102 are inserted into openings 92 in the top flange 86, and the tabs 104 are brought into alignment with and inserted through openings 94 in the side flanges 88. The tabs 104 are similar to tabs 50 and each includes a camming surface 106, a locking shoulder, and a flat ledge, but these face away from the first of engagement at tab 102. The relationship of the camming surface is identical, however, in that upon movement of it past the interfering edge 108 in opening 4 94, respective tension and compresion forces are created between the spaced tab areas of engagement 102 and 104 to hold the elements snug against one another. In this embodiment, element 78 is under compression and the panels 82 of element are under tension.

While only specific embodiments have been disclosed, others are possible without deviating from the inventive concept.

. What is claimed is:

1. A case construction including a pair of adjacent elements interlocked together by spaced areas of engagement, the first area of engagement includes engaging overlying and underlying sections on the respective elements adapted to engage and be biased against one another to interlock, the second area of engagement comprising a tab on one element cooperating with an interfering edge on the other element, the tab having an outer cam surface, an inner cross surface, and an intermediate lock surface, the cam surface sloping relative to the interfering edge such that with the first area of engagement disposed in interlocked relation the outer end edge of the tab can be moved during assembly of the case past the interfering edge without interference until the remaining cam surface engages and rides past the interfering edge to subject the elements to respective tension and compression forces, and whereupon the cross and lock surfaces then simultaneously engage the interfering edge to maintain the elements under the respective tension and compression forces and interlocked together.

2. A case construction according to claim 1, wherein in the first area of engagement the overlying section is on the one element and the underlying section is on the other element, and wherein the cam surface faces toward said overlying section.

3. A case construction according to claim 1, wherein in the first area of engagement the underlying section is on the one element and the overlying section is on the other element, and wherein the cam surfaces faces away from said underlying section.

References Cited UNITED STATES PATENTS 2,503,967 4/1950 Pavelka 220-46 X 2,724,968 11/1955 Greene 22018X FOREIGN PATENTS 290,002 7/ 1953 Switzerland.

GEORGE E. LOWRANCE, Primary Examiner 

